1. Technical Field
The invention relates to the acquisition and digital storage of coloured geographical maps and retrieval thereof.
2. Prior Art
Conventional geographical maps on paper are ill-suited to numerous needs which are increasing at the present time, for example the preparation of long distance missions: each manuscript map can only represent a very limited area, all the more reduced when the map is on a larger scale. The discontinuities represented by the frontiers between maps hinder the preparation of an overall plan.
In theory, nothing opposes acquisition and digital storage of geographical maps on paper: it is sufficient to capture and digitize images as pixels with a scanner. Such a storage is faced with the problem of the volume of data of be stored and, in addition, it does not solve the problem of passing from one map to an adjacent map.
Numerous processors for automatically converting maps into computer-storable form have already been suggested. Reference may for instance be made to the paper by P. J. Min "Computer-aided mapping technology for geographic data base", Proceedings of the S.I.D., Vol. 14, No. 1, 973, pp. 18-25, which describes a vectorial approach for converting map manuscripts into a form which is computer-readable and makes it possible to creating hard copy map outputs. Another approach, which involves a full analysis for feature extraction and consequently requires a very complex system, is disclosed in the paper by R. L. Stanford et al "The application of knowledge base and digital image analysis techniques to automated map interpretation", Proceedings of SPIE, Applications of Artificial Intelligence VI, Orlando, Fla., Apr. 4-6, 1988, Vol. 937, pp. 402-410, SPIE, 1988, Washington U.S.
The prior art methods have one or more of the following shortcomings: they require a complex computing device; the volume of data to be stored for a proper recovery of a colour map is very high; there is no easy possibility to display portions of the map with more than one predetermined definition.